Isoelectric focusing of serum in genetic counselling of families with cystic fibrosis.

The high incidence of carriers of cystic fibrosis in the general population allows application of a less than perfect test to genetic counselling of relatives of children with the disorder and their spouses. In the absence of a definitive carrier detection test, we employ isoelectric focusing of serum in this way and include the a priori chance of carrier status in calculating the risk. The test will eventually be replaced but for the present is preferable in our hands to counselling based simply on the known gene frequency.